Box select doesn't select short edges
This is because when zoomed out, floating point errors cause incorrect detection of what edges are visually obstructed by other geometry when the edges are small compared to their size on screen.
You can get around this by going into a view mode where visually obstructed geometry may be selected.  Either x-ray or wireframe mode will do this.  It's unfortunately not a prefect solution but I find it works fine most of the time.